Fin and tube heat exchanger

ABSTRACT

A metal fin and tube heat exchanger comprising laterally adjacent tubes and a helical fin around each tube in which each fin tip is closely adjacent the tip of the next fin so that shifting of the tube and its fin under thermal expansion and contraction tends to cause internesting and interlocking of these adjacent tips, and a helical metal strip around and engaging each fin adjacent its tip. Each strip has a pitch differing from that of its fin to provide barriers that block internesting and interlocking of the adjacent fins on relative movement between the adjacent fins.

United States Patent Huggins Feb. 22, 1972 [54] FIN AND TUBE HEATEXCHANGER [21] Appl. No.: 122,757

[52] U.S.Cl ..165/172, 165/69, 165/182, 165/ 184 [51] Int. Cl ..FZS! H36[58] Field ofSearch ..165/69, 162, 172, 182, 184, [65/67 [56] ReferencesCited UNITED STATES PATENTS 3,249,154 5/1966 Legrand ..165/164 3,326,2826/1967 .lenssen ..165/172 FOREIGN PATENTS OR APPLICATIONS 130,895 1/1949Austria ..165/172 335,36] 3/1921 Germany ..165/172 PrimaryExaminer-Albert W. Davis, Jr. AnomeyHofgren, Wegner, Allen, Stellman &McCord [57] ABSTRACT A metal fin and tube heat exchanger comprisinglaterally adjacent tubes and a helical fin around each tube in whicheach fin tip is closely adjacent the tip of the next fin so thatshifting of the tube and its fin under thermal expansion and contractiontends to cause internesting and interlocking of these adjacent tips, anda helical metal strip around and engaging each fin adjacent its tip.Each strip has a pitch differing from that of its fin to providebarriers that block internesting and interlocking of the adjacent finson relative movement between the adjacent fins.

8 Claims, 6 Drawing Figures PAIENTuFa22 m2 SHEET 1 [IF 2 INVENTOR.

ATTORNEYS.

PAIENTEDFEBZZ m2 3.643 735 SHEET 2 OF 2 FIG4 FIG5

FIN AND TUBE HEAT EXCHANGER SUMMARY OF THE INVENTION One of the featuresof this invention is to provide a metal fin and tube heat exchanger inwhich the tubes are laterally adjacent each other for flow over andaround the tubes of the first fluid for heat exchange with the secondfluid within the tubes, each tube being provided with a helical fin toaid the heat transfer and with at least some of the fins each having ahelical metal strip engaging the fin adjacent its tip and of a pitchdiffering from that of its fin tip to provide barriers that preventinternesting and interlocking of the tips on relative movement betweenadjacent tube and fin assemblies.

Other features and advantages of the invention will be apparent from thefollowing description of certain embodiments thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view ofone embodiment of the invention.

FIG. 2 is a view similar to FIG. I but illustrating a second embodiment.

FIG. 3 is a fragmentary side elevational view of one of the embodimentsillustrating the invention.

FIG. 4 is a view similar to FIG. 3 but illustrating a furtherembodiment. I

FIG. 5 is an enlarged sectional view taken substantially along line 5-5of FIG. 4.

FIG. 6 is a semidiagrammatic fragmentary end elevational view of afurther embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment of FIG. 1 thetube and fin assemblies 10 each comprising a metal tube 11 and a helicalfin l2 therearound and attached thereto are positioned so that theassemblies are in parallel rows that are parallel to the direction ofairflow as indicated by the arrows 13. Thus the air comprises one fluidthat is in heat transfer contact by way of the tubes 11 and fins 12 witha second fluid such as water flowing within the tubes 11.

In FIG. 2 the tube and fin assemblies 10 are the same as those of FIG. 1but here they are arranged in tandem in relation to the airflow 14.

As is illustrated in the embodiment of FIG. 3 the tips or edges 15 ofthe fins are closely adjacent to each other. Any shifting of theassemblies relative to their neighbors and particularly shifting due tothermal expansion and contraction would ordinarily tend to cause the fintips to internest and interlock and thereby interfere with each other aswell as tend to cause damage to the fins. This problem occurs in verylarge tube and fin structures where the tubes are either horizontal orinclined as they tend to sag thereby bringing the fin edges or tips intocontact with each other. The damaging interengagement of fin tips isalso particularly acute when one tube of an adjacent assembly issubjected to temperatures that are considerably different from thetemperatures of adjacent tubes. In an attempt to solve this problem tubesupports have been tried and even cylindrical sleeves around the fintips have been proposed. All of these, however, have been found to beunsatisfactory, as either not preventing the problem or interferringwith the proper heat transfer and with the necessary fluid flow over andbetween the fins and tubes.

FIG. 3 illustrates one embodiment of a solution to this problem. As isillustrated there, the helical fins 12 around each tube 11 are eachprovided with a helical metal strip 16 attached to the fins 12 adjacenttheir tips 15. Each helical strip 16 is of a pitch differing from thatof the fin tip 15 with the result that the strip provides an effectivebarrier as illustrated in FIG. 3 to prevent the tips 17 of one fin 12from being shifted into the space between the tips 15 of the next setwith possible damage and malfunctioning of the heat exchanger.

In the preferred construction as illustrated in FIG. 3 the helix of themetal barrier strip extends counter to the direction of the helix of thefin 12. Thus when viewed from the left of FIG. 3 the helix of the fin 12is counterclockwise to the tube 11. The helix of the barrier strip 16,on the other hand, is clockwise to the tube 11 as viewed from the leftside of FIG. 3.

The metal barrier strip 16 may be either a flat narrow ribbon as in FIG.3 or a wire 18 as in the embodiment of FIG-5. Regardless of the form ofthe strip it is preferably metallurgically bonded to the metal of thefin 12 as by welding, soldering, brazing or the like in order to secureit fixedly in position and also to provide an additional heat transfermember having efficient heat transfer connections between the barrierstrip and the fin tips.

In the embodiment of FIGS. 4 and 5 the fin adjacent its tip 20 isprovided with a succession of metal tabs 21 struck from the fin 19thereby leaving an opening 22 that extends generally radially from thetube 23. These tabs 21 engage the next adjacent turn of the fin 20 andare preferably themselves arranged in a helix as shown in FIG. 4. Theends of these tabs are metallurgically bonded to the next turn of thefin so as to provide a strong additional barrier and also to providemore efficient heat transfer between successive turns adjacent the fintips 20. As illustrated in FIGS. 4 and 5 there may also be provided anadditional barrier strip 18 of the type described in connection with thebarrier strip 16 that also aids in preventing internesting andinterlocking engagement of the successive fins which as described and asdisclosed in FIG. 3 are closely adjacent each other.

In the preferred construction the succession of tabs 21 is arranged in ahelix that is substantially diametrically opposite the helical barrierstrip 18. As stated earlier, this barrier strip I 18 may be in the formof a wire as illustrated in FIG. 5 or a flat ribbon.

With both the-strip l8 and the helically arranged tabs 21 acting asbarriers there can obviously be considerable shifting of the tubeand'fin assemblies relative to each other without substantialintemesting or interlocking.

The barrier strips of this invention not only provide efficientinterlocking and intemesting barriers but such structures can bemanufactured automatically with the proper equipment and also requireless labor to install than the conventional tube and fin heat exchangerassemblies. In addition, because the fluid such as the air can passeasily between the turns of the helicalbarriers there is 'no substantialinterference to fluid flow. As mentioned earlier, when the barrierstrips are metallurgically bonded to adjacent fin turns they provideadded heat transfer paths and surfaces as well as promoting additionalturbulence, all of which increases the total heat transfer coefficient.

A very important advantage of the invention is that now assemblies ofmultiple row tube and fin structures 24 can be bent to a desiredcurvature as is illustrated inFIG. 6. It is obvious that in bending suchmultiple rows the assemblies must be free to move relative to each otherbecause all of the assemblies are bent to different radii. The provisionof the helical barrier strips 25 of the type already described permitsthis bending of the tube and fin structures 24 in unison whilepreventing the intemesting and interlocking of adjacent fins 26. Thuswith this invention it is now possible to bend many tube and'fin coressimultaneously while before it was necessa ry to bend each coreindividually to the required radius. This is obviously a considerablesaving in time and labor.

Having described my invention as related to the embodiment shown in theaccompanying drawings, it is my intention that the invention be notlimited by any of the details of description, unless otherwisespecified, but rather be construed broadly within its spirit and scopeas set out in the ap pended claims.

I claim:

I. A metal fin and tube heat exchanger, comprising: a plurality oflaterally adjacent tube sections; a helical fin on each tube sectionattached thereto and extending therearound to provide an assembly, theouter tip of each fin being closely adjacent the tip of the next fin;and a helical metal strip engaging each said fin adjacent its tip of apitch differing from that of its said fin tip to prevent internestingand interlocking of said tips on relative movement between said adjacentassemblies.

2. The heat exchanger of claim 1 wherein the helix of said metal stripextends in a direction counter to the direction of the helix of the finengaged by the metal strip and has a pitch greater than that of its fintip.

3. The heat exchanger of claim 1 wherein said metal strip comprises aflat metal ribbon.

4. The heat exchanger of claim 1 wherein said metal strip comprises awire.

5. The heat exchanger of claim 1 wherein each fin tip is provided with atab struck from the fin and engaging the next successive turn of the finadjacent the tip to provide a succession of tabs as further barriers tosaid internesting and interlocking, said succession of tabs beingarranged in a helix.

6. The heat exchanger of claim 1 wherein said helical metal strip ismetallurgically bonded to its said fin.

7. The heat exchanger of claim 6 wherein the helix of said metal stripextends in a direction counter to the direction of the helix of the finengaged by the metal strip and has a pitch greater than that of its fintip.

8. The heat exchanger of claim 7 wherein each fin tip is provided with atab struck from the fin and engaging the next successive turn of the finadjacent the tip to provide a succession of tabs as further barriers tosaid internesting and interlocking, saidsuccession of tabs beingarranged in a helix.

1. A metal fin and tube heat exchanger, comprising: a plurality oflaterally adjacent tube sections; a helical fin on each tube sectionattached thereto and extending therearound to provide an assembly, theouter tip of each fin being closely adjacent the tip of the next fin;and a helical metal strip engaging each said fin adjacent its tip of apitch differing from that of its said fin tip to prevent internestingand interlocking of said tips on relative movement between said adjacentassemblies.
 2. The heat exchanger of claim 1 wherein the helix of saidmetal strip extends in a direction counter to the direction of the helixof the fin engaged by the metal strip and has a pitch greater than thatof its fin tip.
 3. The heat exchanger of claim 1 wherein said metalstrip comprises a flat metal ribbon.
 4. The heat exchanger of claim 1wherein said metal strip comprises a wire.
 5. The heat exchanger ofclaim 1 wherein each fin tip is provided with a tab struck from the finand engaging the next successive turn of the fin adjacent the tip toprovide a succession of tabs as further barriers to said internestingand interlocking, said succession of tabs being arranged in a helix. 6.The heat exchanger of claim 1 wherein said helical metal strip ismetallurgically bonded to its said fin.
 7. The heat exchanger of claim 6wherein the helix of said metal strip extends in a direction counter tothe direction of the helix of the fin engaged by the metal strip and hasa pitch greater than that of its fin tip.
 8. The heat exchanger of claim7 wherein each fin tip is provided with a tab struck from the fin andengaging the next successive turn of the fin adjacent the tip to providea succession of tabs as further barriers to said internesting andinterlocking, said succession of tabs being arranged in a helix.